/*******************************************************************************
 *
 * File Name:          SetCharacterEncodingFilter.java
 *
 * Created:            2006-8-17 23:32:21
 *
 * Original Author:    yu.peng
 *
 *------------------------------------------------------------------------------
 * MODIFICATION HISTORY
 *------------------------------------------------------------------------------
 * WHEN                WHO                 WHY
 * 2006-8-17 23:32:21  yu.peng             new
 *------------------------------------------------------------------------------
 *
 ******************************************************************************/
/*******************/
/* PACKAGE SECTION */
/*******************/
package org.njo.webapp.root.filter;

import javax.servlet.*;
import java.io.IOException;

/**
 * TOMCAT在缺省的情况下使用的时ISO-8859-1的编码集.
 * 为了使整个web应用程序支持其他的编码集而制作的过滤器.
 *
 * @author yu.peng
 * @version 0.01
 */
public class SetCharacterEncodingFilter implements Filter {

    // ----------------------------------------------------- Instance Variables

    /**
     * The default character encoding to set for requests that pass through
     * this filter.
     */
    protected String encoding = null;


    /**
     * The filter configuration object we are associated with.  If this value
     * is null, this filter instance is not currently configured.
     */
    protected FilterConfig filterConfig = null;


    /**
     * Should a character encoding specified by the client be ignored?
     */
    protected boolean ignore = true;

    // --------------------------------------------------------- Public Methods

    public void destroy() {
        this.encoding = null;
        this.filterConfig = null;
    }


    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain)
            throws IOException, ServletException {

        // Conditionally select and set the character encoding to be used
        if (ignore || (request.getCharacterEncoding() == null)) {
            String encoding = selectEncoding(request);
            if (encoding != null)
                request.setCharacterEncoding(encoding);
        }

        // Pass control on to the next filter
        chain.doFilter(request, response);
    }


    /**
     * Place this filter into service.
     *
     * @param filterConfig The filter configuration object
     */
    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
        String value = filterConfig.getInitParameter("ignore");
        if (value == null) {
            this.ignore = true;
        } else if (value.equalsIgnoreCase("true")) {
            this.ignore = true;
        } else if (value.equalsIgnoreCase("yes")) {
            this.ignore = true;
        } else {
            this.ignore = false;
        }
    }


    // ------------------------------------------------------ Protected Methods
    protected String selectEncoding(ServletRequest request) {
        return (this.encoding);
    }
}
